Load control mechanism for self-propelled working machine

Abstract

A self-propelled working machine, which performs work by using power of an internal combustion engine 10 and travels by using power of an electric motor 30 , includes a mechanical governor 75 for maintaining the engine at a designated engine rotational speed Nf. A load control mechanism for the working machine has a maximum working output calculator that calculates a maximum working output Qf from the designated engine rotational speed, an actual working load calculator that calculates an actual working load Qr from the designated engine rotational speed Nf and a detected actual engine rotational speed Nr, and a limit speed calculator that calculates a limit speed Vc from the maximum working output Qf and the actual working load Qr. A travel controller operates and controls the electric motor 30 by setting a travel speed V to the limit speed Vc when the actual engine rotational speed Nr is decreased to be lower than the designated engine rotational speed Nf. The travel speed of the working machine is automatically controlled so that the working load is calculated from the driving condition of the internal combustion engine to ensure the working load to be appropriate. Thus excellent finish of the working is maintained and the operator is relieved from burden.

1. A load control mechanism for a self-propelled working machine that performs work by using power of an internal combustion engine, travels by using power of an electric motor, and includes a governor for maintaining the internal combustion engine at a designated engine rotational speed, wherein:
 the governor is a mechanical governor that mechanically controls a throttle opening of the internal combustion engine; and 
 the load control mechanism comprises: 
 a maximum working output calculating means that calculates a maximum working output from the designated engine rotational speed; 
 an actual working load calculating means that calculates an actual working load from the designated engine rotational speed and a detected actual engine rotational speed; 
 a limit speed calculating means that calculates a limit speed from the maximum working output and the actual working load; and 
 a travel controller that operates and controls the electric motor by setting a travel speed to the limit speed when the actual engine rotational speed is decreased to be lower than the designated engine rotational speed. 
 
     
     
       2. The load control mechanism for the self-propelled working machine according to  claim 1 , wherein:
 the maximum working output calculating means and the actual working load calculating means previously store a no-load output characteristic, which is a relationship between engine rotational speed and no-load output during a no-load driving, and a working output characteristic, which is a relationship between engine rotational speed and working output for every designated engine rotational speed during working, and 
 the maximum working output calculating means and the actual working load calculating means calculate the maximum working output and the actual working load on the basis of the no-load output characteristic and the working output characteristic. 
 
     
     
       3. A load control mechanism for a self-propelled working machine that performs work by using power of an internal combustion engine, travels by using power of an electric motor, and includes a governor for maintaining the internal combustion engine at a designated engine rotational speed, wherein:
 the governor is an electronic governor that electronically controls a throttle opening of the internal combustion engine; and 
 the load control mechanism comprises: 
 a maximum working output calculating means that calculates a maximum working output from an upper limit throttle opening and the designated engine rotational speed; 
 an actual working load calculating means that calculates an actual working load from the designated engine rotational speed and a detected actual throttle opening; 
 a limit speed calculating means that calculates a limit speed from the maximum working output and the actual working load; and 
 a travel controller that operates and controls the electric motor by setting a travel speed to the limit speed when the actual throttle opening is increased to be equal to or higher than the upper limit throttle opening. 
 
     
     
       4. The load control mechanism for the self-propelled working machine according to  claim 3 , wherein:
 the maximum working output calculating means and the actual working load calculating means previously store a no-load output characteristic, which is a relationship between engine rotational speed and no-load output during no-load driving, and a working output characteristic, which is a relationship between a throttle opening and a working output for every specific engine rotational speed during working; and 
 the maximum working output calculating means and the actual working load calculating means calculate the maximum working output and the actual working load on the basis of the no-load output characteristic and the working output characteristic.